1. Field of the Invention
The present invention relates to improvement of a dental root canal diagnostic and treating equipment having a root canal length measuring function.
2. Description of the Prior Art
For treatment of root canal in dental practice a root canal instrument such as reamer or file is used for enlarging the root canal. The depth of the root canal enlargement, which is called "working length", is generally preferred to be up to -0.5 mm (up to 0.5 mm short of an apical position). It is, however, a usual practice that the operator sets it at a position considered optimum on the basis of his experience and in accordance with the therapeutic policy determined for the case or the technique selected therefor and in some extreme cases it is possibly set at -1 mm. When the operator does root canal enlargement by the use of a root canal diagnostic and treating equipment having a root canal length measuring function, it is necessary to do it confirming the position of the tool's tip by means of the display element of the equipment and stop the operation when his preset position has been reached.
With this kind of prior art equipment, however, generally used as display element is an analog meter of the pointer type or a like photoelectric meter. This type of meter is so designed that the displayed value increases steadily as a measuring electrode is inserted into the root canal and it agrees with the reading showing the apical position when the electrode has reached the apical position and has no function of displaying the working length set short of the apical position or of arbitrarily setting this working length.
Also, when a scaler of the ultrasonic type is used, it is necessary to stop or reduce the output of ultrasonic wave a little short of the aforementioned working length, but no conventional equipment has a function of setting and displaying the position at which the output is to be stopped or reduced ("changed" hereinafter). This output changing position is to be set as necessary according to the operator or his treating policy, the change is to be made according to the case, root canal condition, thickness of file used and whether the work to be done is enlargement or washing, and this change is done relatively frequently. Especially, since this root canal enlargement and washing by ultrasonic wave is known to be highly efficient, there is an increased risk of irregular enlargement taking place in the vicinity of the apical position when the output changing position cannot be grasped definitely or of steps or ledges being formed with the output changing position as boundary.
With a prior art equipment without function of displaying the working length or output changing position, therefore, it was necessary to proceed with the operation carefully grasping the position of the tip of the root canal instrument such as reamer or file by means of the display element and to change the output of ultrasonic wave or stop the operation at the present output changing position or working length without fail. This resulted in increased difficulty of operating the equipment and increased burden on the operator as well as lowering of the efficiency of diagnosis and treatment.